8.24 Lidar to Support Ground-Based Astronomy

1. RESEARCH INSTRUMENTATION AND NEEDS Astronomers using ground-based telescopes are necessarily engaged in negating the effects of the earth’s atmosphere, which acts as a wavelength dependent, spatially and temporally non-stationary refractive optical element in any ground based telescope system. Almost all of the extinction of starlight due to aerosols happens in the troposphere. These tropospheric aerosols cause highly variable extinction, and while astronomical sites incorporate ingenious techniques for estimating it, such as dedicated photometric telescopes and radiometers, none of these observatories directly and continuously measure the tropospheric transparency by measuring the atmosphere itself.